aggression vs enmity

aggression and enmity both are nouns.

Word	Noun	Adjective	Verb	Adverb
aggression	Yes	No	No	No
enmity	Yes	No	No	No

As nouns, enmity is a hypernym of aggression; that is, enmity is a word with a broader meaning than aggression:

Other hypernyms of aggression include hostility, ill will.

aggression (noun)	enmity (noun)
violent action that is hostile and usually unprovoked	the feeling of a hostile person
deliberately unfriendly behavior	a state of deep-seated ill-will
the act of initiating hostilities
a disposition to behave aggressively
a feeling of hostility that arouses thoughts of attack